As for system semiconductors (accounting for 80% of the semiconductor industry) represented by a micro-processor unit (MPU) of a PC and a mobile device such as a smartphone, the most important thing to secure competitiveness is a device with high integration (Moore's law), high speed of data processing, high functionalization, and low power consumption. Particularly, as the device is decreased in size, a critical dimension of an interconnect for transferring data to the outside and supplying power to a transistor is decreased, and, thus, lowering a dielectric constant (k) of an interconnect or interlayer dielectric is essential to suppress an interconnect delay or RC delay caused by the decrease of the critical dimension and also to reduce power consumption.
Low-dielectric materials may be roughly classified into inorganic materials and organic materials depending on a material, and film forming methods may be classified into a chemical vapor deposition (CVD) method and a spin-on coating method. The CVD method has the advantage of a small additional cost for equipment investment since the existing equipment can be used as it is. However, when a low dielectric film is formed by the CVD method, it is difficult to control a pore size due to random characteristics of the process. Therefore, during a next-generation device process in need of a process for an interconnect of 25 nm or less, the CVD method is less likely to decrease a dielectric constant to 2.3 or less and cannot satisfy a gap-fill characteristic, and, thus, further application thereof is uncertain. Carbon doped oxide for the CVD method may be Black Diamond II™ from Applied Materials and Aurora ULK having a dielectric constant of about 2.5, and has an elastic modulus in the range of 5 GPa to 9 GPa. Recently, the development of Black DiamondIII™ has been reported. However, it is currently known as having failed in application to a process.
Meanwhile, the spin-on method such as a nanotemplating technique developed by IBM has received attention as a method to overcome the limitation of the CVD method. The spin-on method is capable of forming a large-area film and introducing several nanometer-sized pores into the film, and, thus, can easily decrease a dielectric constant. Since the spin-on coating method can easily control a dielectric constant according to an amount of pores, it is expected to be widely used.
Representative organic porogens used to introduce pores into a film may include hyperbranched polyester [C. Nguyen, C. J. Hawker, R. D. Miller and J. L. Hedric, Macromolecules, 33, 4281 (2001)], ethylene-propylene-ethylene tri block copolymer (Pluonics™) [S. Yang, P. A. Mirau, E. K. Kin, H. J. Lee and D. W. Gidley, Chem. Mater., 13, 2762 (2001)], and polymethylmethacrylate-N,N-dimethylaminoethyl methacrylate copolymer [Q. R. Huang, W. Volksen, E. Huang, M. Toney and R. D. Miller, Chem. Mater., 14, 3676 (2002)]. However, in the case of using the above-described materials as porogens, if a porosity reaches about 15% or more due to phase separation, an interconnected pore structure is formed, which may cause a remarkable decrease in mechanical strength of a film. Therefore, in order to prepare an ultra low dielectric film having an excellent mechanical strength, it is urgent to develop a new concept porogen capable of suppressing phase separation occurring when a matrix is cured and thus minimizing a decrease in mechanical strength according to an amount of pores.
In this regard, the present inventors prepared a reactive porogen using a cyclic sugar compound, and also used the reactive porogen to prepare an ultra low dielectric film having excellent mechanical properties with an increased void content unlike conventional non-reactive porogens, such as polycaprolactone, tetronix, methyl cyclodextrin, and the like [Korean Patent Application Nos. 2004-10927 and 2004-43668]. However, as for a conventional reactive porogen using a cyclic polyol compound such as cyclodextrin and glucose, carbon residue remains even after pyrolysis during preparation of an ultra low dielectric film. Therefore, it becomes a problem when being actually applied to a semiconductor copper interconnect process.